MIL-DTL-5541F Chemical Conversion Coatings on Aluminum and ...

<strong>MIL</strong>-<strong>DTL</strong>-<strong>5541F</strong>
(see 6.4), the chemical conversion coating shall be applied nonelectrolytically by spray, brush, or
immersion after all heat treatments and mechanical operations such as forming, perforating,
machining, brazing, and welding have been completed (see 6.11 and 6.14). Assemblies
containing nonaluminum parts that may be attacked, embrittled, or damaged in any way by the
conversion coating process shall not be coated as assemblies unless the nonaluminum parts are
masked.
3.4 Touch-up. If specified in the contract or order, mechanically damaged areas from
which the coating has been removed shall be touched up or rejected. The damaged areas shall be
touched up with <strong>MIL</strong>-<strong>DTL</strong>-81706 material approved on QPL-81706 for the applicable type,
class, form, and method. The area to be touched up shall be not greater than 5 percent of the
total item surface area (see 6.4 and 6.17).
3.5 Appearance. The chemical conversion coating shall be continuous in appearance and
visibly discernible in daylight. It shall be free from areas of powdery or loose coating, voids,
scratches, flaws, and other defects or damages which reduce the serviceability of parts or are
detrimental to the protective value and paint bonding characteristics. The size and number of
contact marks shall be minimal, consistent with good practice. If specified in the contract or
order, contact marks shall be touched up with <strong>MIL</strong>-<strong>DTL</strong>-81706 material approved on QPL-
81706 for the applicable type, class, form, and method to prevent localized corrosion (see 6.4
and 6.8).
3.6 Performance characteristics.
3.6.1 Corrosion resistance. At the end of 168 hours of exposure to the 5 percent salt spray
test specified in 4.4.1, test specimens (see 4.2.2) treated with the applicable class of coating shall
meet the following corrosion resistance requirements (see 6.14):
a. No more than 5 isolated spots or pits (see 6.9), none larger than 0.031 inch in diameter,
per test specimen. Areas within 0.25 inch from the edges, identification markings, and
holding points during processing or salt spray exposure shall be excluded. Loss of color
shall not be cause for rejection.
b. No more than 15 isolated spots or pits, none larger than 0.031 inch in diameter, on the
combined surface area of all five test specimens, subjected to the salt spray test.
3.6.2 Paint adhesion (wet tape). When the production paint system (6.13) or the paint
system specified in 4.2.2.1.1 is applied to the applicable test specimens (see 4.2.2), no intercoat
separation shall occur between the paint system and the conversion coating, or between the
conversion coating and the base metal, when tested in accordance with 4.4.2 (an adhesion rating
of 4A or better according to ASTM-D3359 Procedure A) (see 6.12). If the conversion coated
parts do not require painting for end use, the paint adhesion test may be omitted if specifically
authorized by the acquisition activity (see 6.4).
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